widest tire for 77 KZ650B

Hello,

I last year bought a stock tire for my kz650 and would like to get a wider tire on the back.

I was curious if anyone knew what the widest tire is that I could put on a stock rim safely. I'd like the biggest tire size possible without compromising safety. The rim is spoked if that makes any difference.

Could you please specify what units you are referring to the tire width.

130 is the widest that will fit. Stock is a 110. With the 130 you might have to notch your chain guard (or eliminate it) to keep the tire from just barely rubbing on the inside of the chain guard. Also, the 130's profile will change quite a bit because it's stuffed onto the 110 rim, it gets quite a bit more round on the crown. I've run like this for 2K+ miles without issue (other than ruining a chain guard)

I ran 130 for years and aside from the chain guard problem (which is a thrill!) they were ok. BUT I now use 120 and I like it better. Less distortion of the tread profile, seems to handle just as well, and is a little easier to mount. Ed

Yea, this has been hashed over here quite a bit. Most agree 120/90-18 is as big as practical on a 2.15" wide wheel. Any wider than that does little good as the rim is too narrow to accomodate the tire. Actually even a 120 is too wide for the wheel, but that's a common size to use. Stock is a 4.00-18. Most places say a 110/90-18 is the "same" as a 4.00-18, but not even close.

Sounds like a really loud version of playing cards in the bike spokes when that chain guard distorts enough to start flapping in the spokes!!! Fortunately I was about 3 blocks from home when it happened to me...

I'll be going back with a 120 when I replace the tire this spring, just want to squeeze the last few safe miles out of the current tire.

I like the 120/90-18 on my KZ650B. Grip wont be a problem, I can hang off her in the turns and she's nowhere near letting go.